The invention relates to drill steel members for a roof drilling system used in mines.
In the mining industry, it is known to support the roof of the mine by drilling vertical holes in the overhead rock strata, and then installing roof bolts into the newly drilled holes. The roof bolts are generally installed into the drilled holes with an adhesive to further secure the bolts within the drilled holes. The bolts secure a metal plate that is positioned to support the rock strata to prevent collapse of the mine roof.
To drill holes in the rock strata, a roof drilling machine is utilized. The drilling machines include a drill driving device and drill steel members. A carbide bit is attached to one end of the final drill steel member, to drill the holes in the mine roof. These drill steel members are generally coupled on the other end to the drill driving device by a chuck located on the drilling machine. This driving device rotates the drill steel member, and thus the drill bit, to remove material and debris from the drilled hole. Many drilling machines incorporate a vacuum suction collection system wherein the drill steel member is a hollow steel bar having a central passage, and the drill bit includes a passageway open to the central passage. The vacuum system collects the debris as it is passed through the bit passageway and the central passage during drilling of the rock strata.
In elevated height mines, the drill steel members are provided with a sufficient length for drilling the desired seam, without the need to replace or extend the drill steel member. In low height mines the hole is initially drilled with a shorter drill steel member, often known as a starter, and then the starter is replaced with additional sections of drill steel, such as drivers, extensions and finishers, to drill the remaining depth of the hole. The additional sections are joined together by component parts that include, for example, a drill bit seat, male and female connectors, and a drive end component. The components are attached or configured to connect to the ends of the drill steel members or sections.
According to one system, a drill steel section is cut to the desired drilling length for a particular member and then the ends of the section are beveled and then component parts are welded onto the corresponding ends of the drill steel section. Many drawbacks for this manufacturing method exist. Welding components and drill sections can induce stress fractures and misalignments.
Other methods have been developed. U.S. Pat. No. 3,554,306 discloses a vacuum drill rod system utilizing tubular members. The tubular members have hexagonal inner and outer cross sectional perimeters which interact with comparable outer and inner cross sectional perimeters of cooperating elements when the rod system is connected to achieve concurrent rotation of the elements of the system. However, this system suffers the drawback that the drill steel rods have hexagonal cross sections that are rotated within the drilled hole. Such rods have been known to cause excessive sound levels within the mine due to the rattling or impact of the hexagonal surface of the drill steel against the round drilled hole.
U.S. Pat. No. 6,189,632 discloses a drilling system utilizing round, hollow drill steel members interconnectable by short components. The short components include a male component machined onto an end of the drill steel member and a corresponding female coupling. The male component comprises an extension with a cross-section defining an external hexagonal perimeter, and the corresponding female coupling element has a cross-section defining an internal hexagonal perimeter, the female component press fit onto the male component. One drawback of this described system is that the drill steel member must be precisely machined to length and must have the aforementioned machined end.
The present inventor has recognized the desirability of providing a drilling system for drilling holes for mine roof bolts which does not require undue machining of the drill steel, which does not require the drill steel to be cut to predetermined lengths and which does not produce excessive noise.
The invention provides an improved drill member, or xe2x80x9cdrill steel,xe2x80x9d for use in a drilling system for installing roof bolts in a mine. The invention provides an improved drilling system incorporating the drill member. The drill member comprises an elongated bar having a central through bore and opposite open ends. The bar has a cross section that defines a circular outside perimeter and a polygonal inside perimeter. The polygonal inside perimeter allows for convenient coupling of the drill member to drill bits at one end and to a motorized drill driving device at an opposite end. The polygonal inside perimeter allows for coupling of the drill members to other drill members using couplings.
The drill members can be cut to any length and the cut open end can accommodate components or interposed couplings without the need for machining a specialized coupling element or configuration onto the member. Additionally, the round outside perimeter allows the drill steel to be more quietly rotated within the drilled hole.
In order to couple the drill steel to the motorized drill driving device, a base assembly is used. The base assembly includes a stub member and a base member. The base member includes a bottom fixture having a cross section defining a polygonal outside perimeter for being received into a correspondingly shaped socket or chuck of the motorized drill driving device. The base member includes a socket having a polygonal inside perimeter. The base member also includes a collar for receiving axial force from the drill driving device.
The stub member includes a bottom fixture having a cross section defining a polygonal outside perimeter that is received into the socket formed in the base member. The stub member further includes a flange that is supported on an internal shoulder within the socket of the base member. In this way, the axial force exerted on the base member by the drill driving device is transferred to the flange of the stub member. The stub member further includes a stub shaft extending upwardly from the flange and having a cross section defining an outside polygonal perimeter, sized and shaped to snugly fit within the open end of the drill member. The socket of the base member is sized such that the drill member fits over the stub shaft and is partially recessed into the socket to press against a top side of the flange of the stub member. In this way, the axial thrust from the base member to the flange is transferred to the end face of the drill member.
Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.